Physics - Rotation Question with Solution | TestHub

The moment of inertia of a solid sphere of radius$\mathrm{R}$about its diameter

${\mathrm{I}}_{\mathrm{s}}=\frac{2}{5}{\mathrm{M}}_{\mathrm{s}}{\mathrm{R}}^2$

The moment of inertia of a disc of radius$2\mathrm{R}$about its diameter

${\mathrm{I}}_{\mathrm{d}}=\frac{1}{4}{\mathrm{M}}_{\mathrm{d}}(2\mathrm{R}{)}^2$

Given,${\mathrm{I}}_{\mathrm{s}}={\mathrm{I}}_{\mathrm{d}}$

$\frac{2}{5}{\mathrm{M}}_{\mathrm{s}}{\mathrm{R}}^2=\frac{1}{4}{\mathrm{M}}_{\mathrm{d}}(2\mathrm{R}{)}^2$

$\frac{{\mathrm{M}}_{\mathrm{s}}}{{\mathrm{M}}_{\mathrm{d}}}=\frac{5}{2}$